Aside from being called "macOS" now, Sierra brings a handful of big new features and a longer list of minor tweaks. We covered most of that ground in our preview of the developer build of the software (and we'll cover it all again in more depth in our full review), but the short list includes Siri, proximity-based Apple Watch unlocking, Apple Pay on the web, and more.

Sierra runs on many current Macs, but for the first time since OS X 10.8 Mountain Lion launched in 2012 Apple is leaving some older hardware behind. The affected hardware is mostly from 2007, 2008, and 2009, so if you've bought something since the turn of the decade you should generally be safe. The full supported list is below:

MacBook (late 2009 and later)

iMac (late 2009 and later)

MacBook Air (2010 and later)

MacBook Pro (2010 and later)

Mac Mini (2010 and later)

Mac Pro (2010 and later)

Features like Handoff require a Mac with Bluetooth 4.0, which began shipping in the 2012 model year. Apple Watch unlocking also requires 802.11ac Wi-Fi, which began shipping in the 2013 model year.

Apple also announced an updated version of its iWork productivity suite, which will include real-time collaboration between multiple users. Apple Worldwide President of Application Product Marketing demonstrated the collaboration functionality on stage at the event, teaming up with a coworker to interactively modify the event's Keynote presentation. No date was announced for the iWork updates, but we're betting it'll be released alongside Sierra in a couple of weeks.

Like every macOS release since Mavericks, Sierra will be a free upgrade for all supported Macs. You can now read our full review of macOS 10.12 Sierra.